Hi guys. We have a 2017 Sienna SE. We had a knocking sound coming from the left rear. I changed the shocks, tried the 3rd row seat adjusting, storage compartments, but nothing worked. By accident I was laying on the ground while my wife moved the car in and out of the garage and I heard the noise from the left sliding door believe it or not. What I did was I loosened the 2 bolts for the door hook and pushed it in just barely, I tightened the bolts and the knocking noise disappeared. I guess it was not pulling in the door tight enough and it was making a knocking/clunking sound. Hopefully that helps.